Adapting To Murder
by ForeverShippingJohnlock
Summary: Sherlock claims to be a highly-functioning sociopath, but as John discovers more about the truth behind the detective's carefully constructed mask, he begins to suspect something much worse. Only one question remains: will John be able to handle what he finds?
1. Suspicions

Chapter 1- Suspicions

John remembers the first time it happened. He had just come home from a long shift at the surgery. Upon walking into 221B he had been shocked to find Sherlock hovering over a messily cut up dead bird, a bloody scalpel in hand. Sherlock hadn't even registered John walking through the door. He just kept staring at the bird, a sort of cold smirk on his face. It made John uneasy.

"Sherlock? What are you doing?" John asked nervously. Sherlock then looked up and, as quick as lightening, the cold look was replaced by the Sherlock equivalent of a reassuring smile.

"Just an experiment, John." He replied, as he packed up the so-called "experiment".

If John had not been so tired, he might have observed that Sherlock looked too cheery, had too much of a bounce to his step, as he went to dispose of the remains of the dead bird, but he didn't. He dismissed the event as just another of his flatmate's insane experiments and went to bed.

What John didn't know, was that this was the start of something that would change both of their lives forever.

The second time it happened, John had just awoken from a particularly bad nightmare. He had gone downstairs to make himself a cup of tea. However, instead of finding his flatmate poring over some case files (which was what he had expected), his face shriveled in disgust as he found the detective standing over a mutilated cat, the same bloody scalpel in hand.

Unlike the bird, these cuts were cleaner, more surgical. As unsettling as it was, the grisly scene wasn't what scared John. What scared him was the twisted smile that Sherlock had on his face, and how his sharp gaze was surveying the cat with what looked like…pride?

John rubbed his bleary eyes, willing what lay in front of him to disappear. When he opened his eyes, Sherlock was still standing there looking insane as ever. Having still not been noticed, John quickly went back upstairs, refusing to believe what he had just seen. The pieces were there, but John couldn't put them together.

He didn't want to.

The third time, John couldn't ignore it. He had come back to 221B after yet another unsuccessful date and what he walked in on was the last thing he was in the mood for. John was no stranger to body parts being displayed in the flat, but that didn't mean he had to like it. So, when he took in the sight of the disembodied head that was currently decorating their kitchen table, he was rightfully frustrated.

_Well, at least he had the decency to put it on a plate first… _John thought bitterly. Just then, Sherlock walked in.

"Date didn't go so well, I presume?" Sherlock said casually, an infuriating smirk on his face. John gave an exasperated sigh and gestured toward the head.

"Sherlock, what the _hell _is this?" John said, purposely avoiding the subject of his date.

"John, I recognize that you may not be a master of deduction, but surely even you could-"

"I _mean_," John said, cutting Sherlock off, "what is it doing _here_?"

"Do you recall my experiment on the coagulation of saliva after death? Well, I wanted to re-test my hypothesis with the assistance of a few new variables." Sherlock replied. John didn't bother with a response and instead just huffed and turned to go upstairs to bed.

"Oh, and John? We're out of milk." Sherlock said. John turned back around.

"And? What do you want me to do about it?" John asked, annoyed.

"Go and pick some up, obviously."

"Why can't you do it?"

Sherlock merely raised an eyebrow. John sighed and pinched the bridge of his nose, repeating the now familiar mantra of _I will not punch my flatmate _over and over again. Just as he was about to tell Sherlock to get his own damn milk, John considered his own ritual of morning tea and how moody he would be without it, so he left for the Tesco, colourful curse words being muttered under his breath.

_Why do I keep doing this? _he wondered on the taxi ride there. John knew the exact answer to that question, but refused to dwell on his not-so-platonic feelings for his flatmate, knowing that it would accomplish nothing but heartbreak. He banished this train of thought as he exited the taxi and entered the Tesco.

As he was scanning the different kinds of milk, John felt someone walk into him.

"I'm so sorry, I wasn't looking! Completely my fault- oh, hello John!" Molly said, picking up the groceries she had dropped. John smiled and bent down to help.

"No problem Molly, how are things?" John asked politely.

"It's been alright, I've been working crazy hours lately. How about you?" she replied.

"It's been fine. We haven't had a case in a while, so Sherlock has been driving me mad with his boredom and his experiments on those body parts you gave him." John said, chuckling. Molly tilted her head and regarded him with a confused expression.

"John, I haven't given Sherlock body parts for over a month…" Molly said curiously. John's whole body tensed up and all of the disturbing scenes he had witnessed over the last couple of weeks came rushing into to the forefront of his mind. He forced a smile onto his face.

"Oh, he must have had some stored in the freezer I suppose." John said. Molly smiled in return.

As they parted ways, John's mind was reeling. He opted to walk home, leg be damned. He desperately needed to think. Questions whirled around and crashed into each other inside his head. Were Sherlock's experiments purely scientific? Was the highly-functioning sociopath label just a façade? Was his best friend really the man that he thought he was? If Molly didn't give him the body parts, where was he getting them?

More importantly, and John shuddered to think it, who did they once belong to?

**Author's Note: I hope this was alright, the idea of psychopath Sherlock is kind of intriguing. I'm planning on making this a longer fic, which I usually don't do, so I'm a bit nervous. Reviews are really really appreciated, they set my mind at ease and give me some confidence so drop me a line :D btw, just to let you know, the title and rating may change!**


	2. Confrontation

Chapter 2- Confrontation

**Author's Note: I'm sooo sorry this has taken me so long! This chapter was WAY harder than I thought it would be, but I worked really hard on it and I'm pretty proud of how it turned out, so I hope you enjoy it :)**

John decided to approach the subject a few days later, after they had just solved a particularly interesting case. Sherlock would be in a better mood and, if ever there were a time to bring it up, it would be then.

The last few days had been difficult to say the least. John had to act completely normal for Sherlock would see through him in an instant. He had to fight the urge to gag or look away every time he saw an "experiment". He was an army doctor after all, and therefore it would look incredibly suspicious if he became squeamish all of a sudden.

Sherlock was sitting hunched over his microscope examining skin cells, presumably taken from one of the many severed fingers sitting beside him in a plastic bag. John took a deep breath.

"So," he started, feigning casualty, "how did you get those? Torture poor Molly again?"

"If you mean manipulating her juvenile feelings for me to my advantage, than yes, I 'tortured' her." he replied, not looking up from his work. John nodded.

"When did you get them?" John asked.

"Last week." Sherlock replied. He looked up and gave John a curious look, "Why?"

John's heart quickened, why was Sherlock lying to him?

"No reason, just wondering." John countered, looking away. Sherlock's curious look quickly turned to one of suspicion.

"Clearly there is a reason, I can read it in your face."

"Sherlock, just leave it." John replied, desperately trying to get out of this situation, but Sherlock had already started walking towards him, his eyes in full deductive mode.

"The most obvious sign is that you are clearly avoiding direct eye contact with me. Your hunched body language suggests that you are trying to make yourself smaller, very odd considering your usual proper stance, that of a soldier. Explanation? You are nervous and afraid. But the question is why?" Sherlock started to pace, his eyes alight with the excitement of a new puzzle. "Your symptoms seemed to escalate when I said about picking up supplies for my experiment from Molly last week. Normally, that wouldn't be much cause for alarm. As a matter of fact, you don't particularly make a habit of questioning the sources of my experiments. So, what's changed? Unless… _oh._" Sherlock paused his pacing and walked back over to where John was glued to the spot. John tried to feign his usual level of annoyance at the detective's dramatics.

"What amazing conclusion did the world's only consulting detective come to this time?" he asked sarcastically, praying that Sherlock wasn't on to him.

Sherlock stepped closer, invading John's personal space. John made the mistake of looking into his eyes. There was something in them, something that John couldn't quite place. The usual intensity was there but there was a new aspect to it, a certain predatorial ferocity that made John incredibly nervous.

"You already know what conclusion I've come to. I suspect you've known for a while." Sherlock said. John decided to play dumb.

"Do I?" John replied. Sherlock let out a huff of annoyance.

"John, don't insult my intelligence. We both know what I'm talking about."

"Are you going to make me say it?" John asked, straightening himself to his full height. Sherlock nodded and then spoke.

"Just know that whatever you ask, I will answer with complete honesty. Are you ready for that?"

John didn't answer his question, for he wasn't quite sure of the answer, but he knew that, whether he was ready for it or not, he needed to know the truth.

"I know you haven't been getting your supplies from Molly, so where are you getting them?" John asked, forcing his voice not to shake. He maintained eye contact. He hoped that Sherlock would dismiss his question as ridiculous, or get angry with John for even considering the possibility. However, that wasn't what happened. It must have been a full minute before Sherlock answered him.

"I killed for them." John gasped at his flatmate's blunt confession. He didn't say anything.

"Are you afraid?" Sherlock asked. John shook his head.

In truth, John wasn't all that afraid. He knew he should be, he knew that Sherlock was dangerous, he knew that he must be mad for even remaining in this flat, but he wasn't afraid of him. John figured that if anything, he was afraid of the uncertainty of the situation. However, now that he knew the truth, the fear had alleviated to simple unease. John didn't know why this was. Maybe he felt that he was unfit to judge. He was a soldier after all, and had killed many people. He obviously didn't approve of his flatmate's extracurricular activities, but he wanted to know more.

"Why are you telling me this?" John asked. Why would Sherlock tell him when he could easily go to the police? Sherlock seemed to ponder his question, as if he were searching for the right words.

"Because John, you're… special."

"Special?" John repeated incredulously.

"Yes. My entire life I have never felt anything for anyone other than irritation and disgust. I resented humanity and thought it to be boring. They meant nothing to me and I felt nothing towards them. But then you came along. You don't bore me, and I find myself… drawn to you. I can tolerate your existence in my life, and sometimes even enjoy it. You are unpredictable. You tend to act the exact opposite of how other people would, and you never cease to surprise me. I trust you. You are my friend John, something I'm sure you know that psychopaths don't frequent. That's why you're special."

John remained quiet throughout this speech. All this time he thought that he was painfully normal. He thought that he was just kept around because he was convenient for Sherlock; someone to fetch him pens and to get the milk. So, to know that he actually meant something to the detective was very surprising and flattering. It also reminded John why he cared for him. The fact that he still felt something for Sherlock, even after his confession, was a rather disturbing question that he wasn't quite ready to tackle just yet. Sherlock looked directly into his eyes, and John saw what looked like a slight vulnerability in them.

"Will you stay? Even knowing what you know? _Can _you stay?" Sherlock asked. John blinked. A sudden realization dawned on him; he hadn't even considered leaving. Not once. He didn't think he could, no matter what Sherlock did in his spare time. John craved adventure; he needed it. Sherlock provided that, and more. He couldn't survive without him. He couldn't leave, even if he wanted to. John smiled at his flatmate.

"Of course I will." John said. He then made his expression more serious. "But first we have to have a few rules."

**Author's Note: Hope it was okay! I didn't want John to be afraid of Sherlock, but I knew that if he wasn't afraid whatsoever that it would be unrealistic… hopefully it wasn't too OOC. Reviews are INCREDIBLY appreciated so please drop me a line! :D**


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